This invention relates generally to the field of hybrid internal combustion-electric powered vehicles and more specifically to machine for augmentation, storage, and conservation of vehicle motive energy.
In the instant specification and claims, the process of installing or including electrical energy augmentation of an internal combustion powered vehicle is referred to as “hybridization”. Vehicles thusly augmented will be referred to as “hybridized.” Further, in the instant specification and claims, the terms “modify,” “sophistication,” and forms thereof exclude such simple and inexpensive processes as drilling holes in extant elements merely to provide anchor points to interface components or to bracket or attach elements to extant components or to run wires. Where used, the term “conventional” indicates an internal combustion engine or vehicle driven thereby.
In this document, the term motor-generator is used to describe a transducer that can function as either an electric motor or a generator, converting electrical power to or from mechanical power, the term transducer describing any device that converts one type of energy to another type of energy.
It has long been known that internal combustion engines operate most efficiently within a narrow range of powers or speeds. However, in normal use, an automobile must climb and descend hills, stop and start, accelerate and brake, or cruise at high speeds on highways. These impose a wide range of power and speed demands on the power plant.
Thus, the internal combustion engine powering such a vehicle often will not be operating within its most efficient parameters. In fact, in the severe stop-and-go situations in which most driving is accomplished, its efficiency is generally quite low. Therefore, alternate drive systems and power sources to increase efficiency are increasingly sought.
One such effective system, popularly known as a “hybrid,” involves combining an electric motor with an internal combustion engine in such a manner as to allow back-and-forth power augmentation and trade-off, permitting the more efficient and effective of the two to provide propulsion within its best operating range as speed and power demands are made and relaxed.
This permits, for example, the electric motor to augment the internal combustion engine to prevent it from having to operate above its preferred power level. In example, when the vehicle must accelerate from a stop to particular speed, the electric motor, which characteristically provides high torque, even at low speeds, is engaged to such degree that the internal combustion engine need not exceed its optimal power output. Also, while at cruise speeds, when acceleration is required, the internal combustion engine may continue to run at its preferred power level while the electric motor adds the required extra power.
The hybrid may also comprise means to convert the electric motor to an electric energy generator when the vehicle is braking or traveling downhill. Employed thus, momentum of the vehicle, and, indirectly, energy from the internal combustion engine, may be used to recharge the battery, cell, or other energy storage device, thereby literally recycling energy that would otherwise be lost.
The hybrid may also have a means to recharge the battery, cell, or other energy storage device by plugging it into an electric power grid. Most recharging could be done at night, during non-peak power demand hours thusly using cheaper, low demand electricity.
In addition, many other benefits, both economic and ecological, well known to those well versed in the art, may accrue due to hybridization of motor vehicles. However, up until now, the high cost to end users of implementing this art has prevented wide scale adoption.
Typically, a hybrid vehicle is designed and manufactured, as a new vehicle from the very beginning, because its manufacture requires inclusion of additional elements. Because the traditional elements of exclusively internal combustion vehicles configurations must be redesigned and specially manufactured to accommodate the additional hybridizing elements, economy of scale may not be achieved.
Further, even if a new hybrid vehicle could be brought to end users at a competitive price, market penetration would be very slow due to the hundreds of millions of conventional vehicles already on the road world-wide, the abandonment of which could not be effected without serious economic disadvantage.
With this in mind, various previous technologies have been proposed to convert extant gasoline powered vehicles to hybrid electrical units. The envisioned solutions typically require placement of one or more electric motors in mechanical communication with the wheels of a given vehicle. These motors are generally tied to an electrical storage battery and a controller similar to the one used in new design-built hybrid vehicles. Such solutions, however, continue to pose significant cost obstacles. The greatest challenge they present is to design an affordable and efficient method for installing the electric motor drive without also re-designing and replacing vast numbers of components already in use.
Typically, the proposed means of meeting this challenge requires replacement or substantial modification of the existing wheel structure, including the wheel bearings and brakes. Because of this replacement, other engineering issues and obstacles arise, such as the location, design and coordination of the electric motors as well as the addition of significant un-sprung (and therefore, excess) weight to the suspension system. These expenses multiply quickly and become cost prohibitive.
The invention taught herein provides means of avoiding this expense, thereby bringing the costs within economically viable parameters. Conversion of present internal combustion powered automobiles to internal combustion/electric hybrids becomes a practical option.
Disclosed herein is a wheel hub motor technology to power vehicles of two, three, or four-wheeled design. In the preferred embodiment, the wheel hub motor is integrated into the structure of existing axle/hub/spindle/brake assemblies. Where previous technologies predominantly employ wheel hub and electric motor configurations that require significant modification and re-design of the associated wheel and hub assemblies to incorporate components such as bearings, axle, and brakes, the herein taught art exploits the existing axle, bearings, brake structure of the associated vehicle, adding the wheel hub motor capability essentially without modifying the existing wheel structure.
The advantages of this approach include: lower cost, simplicity of retrofit, and maintenance simplicity on the electric motor and on the existing brake, bearings and wheel structure. The retrofit addition of easily integrated hybrid components such as battery pack, control electronics, electric motor, and wiring allows “plug-and-go” hybrid conversion for most automobiles.
Preferred embodiments incorporate a rotor and stator. These are constructed of corrosion resistant materials that prevent exposure to normal operating conditions from degrading performance. Reliability of vehicle bearings and brakes is unaffected by the addition of this wheel-hub motor stator and rotor.
This wheel hub motor system presents conveniently few obstacles to routine conventional maintenance requirements. For example, when maintenance to the rear brake assembly is required, the tire/wheel is removed in the normal manner and the rotor is similarly removed from the lug-bolts. Since the stator-plate is located behind the brake spindle assembly, it does not affect the repair procedure.
The rotor and stator assemblies are mechanically simple components that could be produced at low cost in high volume production. System and installation expenses are also avoided because the load bearing and braking function of the wheel as designed by the automotive designer is not changed. Thus this invention largely overcomes the challenge of adding electric motor hybrid power to an existing vehicle without extensive mechanical modification and without significant negative impact on cost, performance, reliability, or maintenance.
Generally speaking, the specified brushless direct current or DC motor design employed offers several advantages. A brushless motor normally has permanent magnets which rotate and a stationary electromagnet. This eliminates significant difficulties that would otherwise result from the necessity of connecting current (via a brush/commutator) to a moving armature. An electronic controller replaces, and performs the same function as, a brush/commutator in a brushed DC motor. This function is the activation of continuous phase switching in the windings, thus keeping the motor in motion.
Other advantages are that brushless DC motors generally offer more torque per unit of weight, improved efficiency and reliability, low maintenance requirements, reduced noise, longer lifetime (largely due to the existence of no brush/commutator to wear out), elimination of brush/commutator sparks, and, accordingly, less overall electromagnetic interference (EMI). Finally, brushless DC motors characteristically exhibit particularly high efficiency in conversion of electricity into mechanical power, particularly under low-load conditions.
A challenge posed in brushless motor design is the fact that a controller must direct and/or detect rotation of the rotor. This requires a means of determining the rotor's orientation/position relative to the stator coils. Known technologies may use Hall effect sensors or encoders to directly measure the rotor's position. Such technologies are well established, and therefore require no other specific details, herein.
Other methods measure electromotive force in the undriven coils to infer the rotor position, thereby eliminating any need for separate Hall effect sensors. Such systems are often called, although somewhat erroneously, sensorless controllers. Such sensorless controllers may face difficulties in starting from a full-stop condition, because with no motion, there is no electromotive force to be measured in the undriven coils.
In any case, the controller, employing a logic circuit, regulates high-current DC power. In a more primitive form, a controller may employ comparators to merely determine when, to advance an output phase. More technically sophisticated controllers may exploit a microcontroller to manage acceleration, to precisely control speed and to fine-tune efficiency.
One mention-worthy potential disadvantage in some brushless designs is that, although the maximum electrical power that can be applied to a brushless DC motor is notably high, it can be subject to significant thermal limitations. Heat, particularly in the case of rare earth magnets, can quickly cause permanent degradation of magnetic qualities. This can pose notable cooling demands.
Inherently in the design of the technology taught herein, this challenge is largely overcome. High volumes of cooling air constantly pass through the device while its associated vehicle is in motion. Thus, copious heat exchange is naturally available to drain off thermal energy. As a rule of thumb, the more power demanded, the more speed is initially produced, and the more cooling air is forced through as a result of the increased speed. Once cruise speed is reached, power demands reduce, but cooling air-flow continues at a high rate.
To direct the description with greater specificity and to address and compare earlier technologies, U.S. Pat. No. 4,165,795 by Lynch et al. and U.S. Pat. No. 4,335,429 by Kawakatsu disclose hybrid drive systems for automobiles wherein an internal combustion engine is augmented by a battery powered electric motor. Both patents teach electric motors and internal combustion engines communicating with common drive shafts. In addition, the electric motors taught by Lynch et al., and Kawakatsu comprise housings, shafts, armatures, and bearings intrinsic to said motors.
In contrast to Lynch et al. and Kawakatsu, the instant art teaches an electric motor fitted on and within an internal combustion powered automobile but not in physical communication with the drive shaft served by the internal combustion engine. The instant art, instead, exploits other non-modified elements normally present in an internal combustion powered vehicle, using these elements to mount or serve as armature, shaft, housing, and bearings.
In further contrast, the instant art teaches a stator and a rotor being held in operative magnetic communication with each other by connective devices which also hold in operable position un-modified original components of an internal combustion vehicle. Thus, the stator and rotor may be added or removed essentially without displacing or otherwise affecting the vehicle's conventional drive system.
U.S. Pat. No. 4,714,854 by Oudet and the monograph, Optimal Design and Control of Axial-Flux Brushless DC Wheel-motor For Electric Vehicles, by Y. P. Yang et al. teach electric motors suitable for hybrid electric and internal combustion powered vehicles. Said motors comprise armatures, shafts, housings, and bearings normally intrinsic to such motors. Thus, these motors may function independently of any other elements of an associated vehicle.
In contrast to Oudet and Yang et al., the instant art exploits non-modified elements normally present in an internal combustion engine powered vehicle to mount, contain, or serve as portions of armature(s), shaft(s), housing(s), and bearings. In further contrast, the instant art teaches a stator and a rotor being held in operative magnetic communication by connective devices which also hold in operable communication un-modified elements normally included in or comprising a conventional vehicle.
Because the instant art incorporates components of an associated vehicle, it may not function independently of the associated vehicle. However, the instant art may be installed on, or removed from a vehicle without requiring replacement parts for, or affecting or disabling the vehicle on which it is or was installed. Simply by disengaging the connective devices and mounts, the elements may be disassociated from the vehicle and the rotor and/or stator may be disassociated from each other. In fact, by simply disconnecting electrical circuits, the associated vehicle may return to function in a purely internal combustion mode, the electrical components remaining in place.
U.S. Pat. No. 5,438,228 by Couture et al.; U.S. Pat. No. 5,600,191 by Yang; U.S. Pat. No. 6,768,932 B2 by Claypole et al.; U.S. Pat. No. 2,514,460 by Tucker; and U.S. Pat. No. 5,157,295 by Stefansky et al. disclose in-hub wheel-motors that require specially designed hub elements to support the in-hub wheel-motors and to transfer force from the in-hub motors to the wheels.
In contrast to Couture et al., Yang, Claypole et al., Tucker, and Stefansky, the instant art requires no specially designed or modified vehicle elements to communicate force from a motor to a wheel. Instead it communicates with the un-modified wheel and wheel support elements normally present in a conventional vehicle.